[PV Panel Quality] Sharp's Accelerated Degradation Test (1)

Test based on data of 30-year application

2014/08/02 21:44
Kenji Kaneko, Nikkei BP CleanTech Institute

Tsubosaka Temple in Takatori-cho, Takaichi-gun, Nara Prefecture, Japan, is the No. 6 temple of the 33 temples that are visited during the Kansai Kannon Pilgrimage. The temple is known for its auditorium and the three-story pagoda built in the Muromachi era, as well as being popular for those praying for cures for eye diseases.

The temple grounds are on a mountainside. In the grounds, there is a large Kannon statue, about 20m in height, which is believed to have been a present from India. You can see the statue from a short distance if you climb the stone steps behind the main building. Two lights were mounted at the bottom of the large Kannon statue in 1983 to illuminate it at night (Fig. 1).

The solar power generation system was incorporated responding to a request of the chief priest at the time to use natural energy to illuminate the Kannon statue"(Fig. 2).

"Solar power panels manufactured by Sharp were installed because the chief priest at that time had close relations with Tokuji Hayakawa, the founder of Sharp Corp," said Shoshin Kita, steward of Tsubosaka Temple.

The power supply system is a stand-alone power system. Electricity generated in the daytime by 40 sheets of 35W solar power panels is stored in lead-acid batteries, and the Kannon statue is illuminated automatically after sunset.

This solar power generation system is currently attracting attention. The "30 years," operating period of the system, is a short period for Tsubosaka Temple, which was established more than 1,300 years ago. The period, however, according to sources, is the longest among operation periods of solar power generation systems in Japan.

Amid the increased interest in renewable energy following the Great East Japan Earthquake, the temple is visited by a number of people from material manufacturers and others. In the research into solar power panel durability, the deterioration condition of the solar panels at the temple provides precious data that cannot be obtained at a laboratory. The solar power generation system at Tsubosaka Temple has also been playing an important role in quality control and development of solar power panels by Sharp.

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Incorporates German VDE quality standard

Sharp established a new quality evaluation standard for solar power panels in September 2013. The standard incorporates the quality evaluation standard established by VDE Testing and Certification Institute, an international third-party certifier for the safety of electrical products. VDE is the largest electrical/electronic technology organization in Germany and establishes the national standards of that country, issues safety certifications and performs tests in respect to electrical products.

The special standards of VDE are based on the long-term reliability test program that VDE developed jointly with the Fraunhofer Institute and the German solar battery industry. The standards are stricter than official quality evaluation standards, and only five companies throughout the world, including Sharp, have been approved by the VDE standard.

The standard specified by the IEC (International Electrotechnical Commission) is one of the international quality evaluation standards for solar power panels. Sharp established its unique "accelerated degradation test" method utilizing the solar power panel data obtained from the 30-year-old panels at Tsubosaka Temple as well as the IEC test items for product development.

In accelerated degradation tests, stress is applied to products to reproduce the deterioration in a short period of time that may occur over a long period. Sharp established the quality evaluation standard that satisfies both the IEC standard and the VDE standard by adding the test items specified by VDE to its own accelerated degradation test. If the products are evaluated based on the standard, they can obtain the VDE certification (Fig. 3).

"It is difficult to determine the quality and long-term reliability of solar panels, unlike the conversion efficiency," said Hideki Yoshioka, who is in charge of quality and environment at the Solar System Division of Sharp. "Even if we explain that we perform a unique evaluation test that is stricter than the IEC test, it may sound self-approving. Therefore, we obtained a certificate from an international third-party certifier for the special quality evaluation standard of Sharp, to ensure a sense of security in respect to the quality and long-term reliability."

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